FIG. 1 shows a schematic of a typical air conditioning system 100 for an HVAC system in a vehicle. The air conditioning system 100 includes a compressor 102, condenser 104, a sub-cooler 106, a thermal expansion valve (hereinafter “TXV”) 108, and an evaporator 110. A refrigerant is cycled through the air conditioning system 100 in the direction indicated by the arrows. The refrigerant cycle involves a three-phase process that includes pressurization, condensation and vaporization, which will be subsequently explained.
At stage 112, before the refrigerant enters the compressor 102, the refrigerant is a low pressure, low temperature gas. In the pressurization phase, the compressor 102 compresses the low pressure, low temperature gas into a high pressure, high temperature gas. Pressurizing the refrigerant causes the refrigerant to become much hotter than the outside air, which ensures that the refrigerant will change from a gas to a liquid in the next phase.
At stage 114, before the refrigerant enters the condenser 104, the refrigerant is a high pressure, high temperature gas. In the condensation phase, outside air drawn over the condenser 104 absorbs the heat contained in the refrigerant to thereby cause the refrigerant to condense into a high pressure, high temperature liquid. The outside air carries the heat that was absorbed in the evaporation phase described below away from the condenser 104.
At stage 116, before the refrigerant enters the sub-cooler 106, the refrigerant is a high pressure, high temperature liquid. The sub-cooler 106 at the exit side of the condenser 104 reduces the temperature of the refrigerant for two reasons. The first reason is to make sure that all of the refrigerant has been transformed from a gas to a liquid. The second reason is to allow the refrigerant to vaporize in the evaporator 110 at a lower temperature thereby allowing the evaporator 110 to work more efficiently. It should be noted that the sub-cooler 106 reduces the temperature of the refrigerant by only a small amount, typically in the range of 5-10° C. Thus, at stage 118, after the refrigerant exits the sub-cooler 106, the refrigerant is still considered a high pressure, high temperature liquid.
Prior to entering the evaporator 110, the refrigerant enters the TXV 108. The TXV serves more than one function. The TXV 108 regulates the flow of refrigerant into the evaporator 110 based on cooling demand. The TXV 108 also reduces the pressure of the refrigerant, which further decreases the temperature of the refrigerant. This allows the refrigerant to vaporize at a lower temperature once in the evaporator 110 to ensure that the refrigerant will absorb the maximum amount of heat. Thus, at stage 120, the refrigerant is a low pressure, low temperature liquid.
In the vaporization phase, a blower (not shown) forces warm air drawn from inside the vehicle over the evaporator 110. The refrigerant removes the heat from the warm air, which causes the refrigerant in the evaporator 110 to boil thereby converting the refrigerant from a liquid to a gas. Thus, the warm air blowing across the evaporator 110 is cooled to a temperature less than a temperature inside the vehicle. The cool air exits through air conditioning vents to the inside of the vehicle at a much lower temperature than the air inside the vehicle thereby cooling the interior of the vehicle. Simultaneously, the heated refrigerant exits the evaporator 110 and the cycle is repeated.
During the vaporization phase, condensation forms on the evaporator because the moisture from the warm air condenses on the cold evaporator. The condensation eventually drains to the ground outside the vehicle. Thus, a disadvantage of the current air conditioning system is that the system loses cooling energy due to the drainage of the condensation that forms on the evaporator.
Therefore, what is required is an air conditioning system that utilizes the lost energy to increase the efficiency of the air conditioning system.